What graphics card should be compatible under Rs4000 for ASUS M3N78EM?

I have at present an AMD Phenom X4 9650 Agena 2.3GHz Socket AM2+ 95W Quad-Core Processor installed on it.. with a 400w power supply.. I have very low budget under rs 4000.. any suggestions?? would 400w be sufficient or modding is needed?? .. its tough to think out to sale a some what old setup at this moment.. unless I get a job.. .. hard on wallet situation.. just need a card for upgrading the motherboard.. any suggestions within this budget would be cool..?? ..